Method of cleaning mold parts



Patented Nov. 1, I932 UNITED STATES PATENT: OFFICE JOHN M. PORTER AND GEORGE W. HANDY, OF ELIZABETH, NEV JERSEI'ASSIGNORS TO STRUCTURAL GYPSUM CORPORATION, OF LINDElL NEW JERSEY, A CORPORATION OF DELAWARE No Drawing.

D In the patent to Ruby, No. 1,692,420, dated November 20, 1928, there is disclosed a continuous machine for the casting ofblocks or tiles from wet gypsum mixes and in the operation thereof it has been found that the nzold parts and particularly the core poles, become coated with a slight film of the set gypsum material. This film oftentimes builds up gradually to the point, that, as the core poles are pulled from the blocks they have a tendency to resist the pulling action to such an extent that the blocks may be partially crushed against the mold-heads. It is extremely desirable, therefore, that the mold parts which, in the Ruby machine are made of aluminum or aluminum alloy, be maintained clean and bright or be cleaned from this adhering film periodically before the film reaches a thickness where it will cause trouble,

To this end the invention has forits prin cipal object a method of causing the plastic material in a mold to readily free itself from the mold. The invention has particular applicability to a process of molding gypsummixes where aluminum mold parts are used.

In carrying out the invention as applied to gypsum where aluminum mold parts are used, it has been found that if-an alkaline material is added to the mix in quantities sufiicient'to produce a reaction between this material and the aluminum mold parts, the

- tlon of an alkali in such proportlons that a parts are freed from the adhering film.

In some instances it may not be desirable to produce a continuous alkaline state in the wet mix and in such cases it will be satisfactory to cause this condition to exist periodically when themold parts have accumulated a film. At that time if the mix be made alkaline the reaction will take place with the alu minum parts and the film removed therefrom.

Any desired alkaline material, which is of a character which will react with the aluminum parts, may be added to the mix and lime METHOD or CLEANING om) Prisms" Application filed September 16, 1929. Serial 110,393,126.

While there hasbeen'here set forth an application of the invention to the casting of gypsum mixes with molds of aluminum, yet obviously the invention is not to be restricted thereto as .it contemplates a method of casting any cementitious material which has a tendency to build up in a film upon the mold parts, by adding to the mix some'substance or substances-Which will react chemically with with thelcastiiig of gypsum in aluminum mold parts it would appear that the freeing ofthe set material from the parts was due to the generation of an infinitesimal amount of'hydrogen upon the surface of the parts, yet this may not be true and the action may be due to some other reaction productbetween a substance in the mix and the mold part.

In the use of calcined gypsum fromsome sources, for instance, the sludge in the phosphoric acid industry, there is usually added atsome point" in the process, lime or other alkali to neutralize the resid'ual'phosphoric acid. 7 This alkali is ordinarily added'to the point where a' slight alkaline reaction results in order to insure that all ofthe phosphoric 7 acid has been neutralized. Such slight alkalinity is not sufficient in most cases to cause a reaction with the mold parts, and hence the invention contemplates the addireaction will result between the same and the mold parts to free the latter from the set material.

Although we have described our invention, setting forth one specific procedure for freeing mold parts from adhering material, our invention is not limited thereto as various means will suggest themselves to those skilled in the art. For example, the lime which We usually use may be replaced by soda, potash, or other alkaline material, and even by materials which may be non-alkaline but which have the property of freeing the mold part from the film. These and other changes may be made in our invention Within the scope thereof, which is defined in the claims appended hereto.

What we claim is:

1. A method of freeing aluminum mold parts in gypsum casting machines which consists in adding to a plastic gypsum mixture a substance which will react with the aluminum mold parts.

2. A method'of freeing aluminum mold parts in gypsum casting machines which consists in adding to a plastic gypsum material a substance which will generate a gas by reaction with the mold parts and charging themixture into a mold. '3. A method of freeing aluminum mold parts in gypsum casting machines from a cast gypsum product, which consists in making a wet gypsum miX alkaline and charging the mixture into an aluminum mold.

l. A method of freeing aluminum mold parts. in gysum casting machines from a cast gypsum product, which consists in adding to a gypsum mixture an alkali and the requisite amount of water and charging the mixture into an aluminum mold.

V 5. A method of casting cementitious materials in aluminum molds which consists in making a plastic material alkaline prior to its introduction into the aluminum molds.

' 6. A methodof continuously casting gypsum in aluminum mold parts which consists in. periodically making a plastic gypsum mixture alkaline prior to its introduction into the aluminum mold. 7. A method of continuously casting gypsum in aluminum molds which consists in adding lime to aplastic gypsum material prior to its introduction into the aluminum mold. V

8. A method of casting gypsum shapes which consists in charging plastic gypsum and lime into an aluminum mold. V

In testimony whereof, we have hereunto subscribed our names this 11th day of September 1929.

JOHN M. PORTER. GEORGE HANDY. 

